Film duplicating apparatus

ABSTRACT

An apparatus for duplicating photographic film of the type wherein original and copy film travel together over a printing drum and are irradiated by exposing light in a printing zone. A combination of rollers act to isolate the films in the printing zone so that film tensions outside the zone are not particularly critical. The surface of the drum is of a relatively low friction material so that the films are free to slip somewhat on the drum as is necessary to prevent relative movement as between original and copy films.

United States Patent 1 Allport 1541 FILM DUPLICATING APPARATUS [75] Inventor: Walter Allport, Stamford, Conn.

[73] v Assignee: Cutler Hammer, Inc., Milwaukee,

Wis.

[22] Filed: Nov. 24, 1971 [21] Appl. No.: 201,643

[52] U.S. Cl. ..355/ll0, 355/90, 355/111 [51 Int. Cl. ..G03b 27/10 [58] Field of Search ..355/l1l, 110, 90, 104,108

[56] References Cited UNITED STATES PATENTS Davis ..3S5/111 Pfaff ..355/111 1 Feb. 6, 1973 2,586,286 2/1952 Andreas ..355/ll1 Primary Examiner-Samuel S. Matthews Assistant Examiner--Richard M. Sheer Attorney-Henry Huff [57] ABSTRACT 7 Claims, 2 Drawing Figures PATENIEDFEB sms 3,715,159

sum 20F 2 FILM DUPLICATING APPARATUS BACKGROUND OF THE INVENTION This invention relates to apparatus for reproducing film and, more particularly, to improvements in apparatus for duplicating microfilm with minimal loss of resolution.

The process of transferring information or data from a master or original film to a raw copy film is commonly known as printing." In the conventional printing operation the two lengths of film involved are brought together in intimate contact over a relatively small portion of their lengths and, while together, exposing light is passed through them. As a result, a copy film, which is light sensitive, is selectively exposed and thereby imparted with the information content of the original film.

A popular type of film printer which is presently in widespread use employs a relatively large, rotating printing drum over which the films pass during printing. Generally, the original and copy films start out on separate supply reels, are brought together for passage over the drum, and then are separated for eventual storage on'separate takeup reels. During transport over the drum every effort is made to keep the original and copy films close together and in fixed registration with respect to each other.

Although drum-type printers perform their desired function, there is much room for improvement in the crucial areas of operating speed and quality of results. Unfortunately, considerations of speed and quality are often countervailing; i.e., gains in one are accompanied by losses in the other. Also, the striving for enhanced performance generally leads to equipment which requires more complex and costly components, such as precision tension-controlling devices.

The operating speed problem exemplifies the type of trade-offs a designerof film duplicating equipment is faced with. High operating speeds are, of course, desirable since, for example, a machine which is capable of duplicating 100 feet of film per minute can.

theoretically do the work of two machines which can duplicate onlySO feet of film per minute. It is equally clear that at higher operating speeds it becomes more difficult to make the films travel smoothly and in registration over the printing drum. Another problem which arises at relatively high printing speeds is that each unit length of film necessarily spends less time in the designated printing zone;-i.e., less time exposed to the printing light. Since it is required that the photosensitive film be exposed to a certain minimum quanta of light, it follows that higher intensity light is needed for higher operating speeds. It is found, however, that the I use of an intense light source generates undesirable heat which acts to expand or deform the films in the printing zone and thereby compound the problem of maintaining registration.

One approach to solving the aforementioned problems has been to keep the copy film (which is the film on'the printing drum with the original film overlapping it) from slipping on the printing drum. The common objective of having the copy film grip the drum during its excursion thereover has been realized by utilizing a drum surface which has a relatively high coefficient of friction with respect to the film. This technique has been somewhat successful, but blurring of duplicates is still found under certain operating conditions. For applications such as microfilm duplication, the presence of even slight blurring in the duplicate is a highly undesirable condition.

Accordingly, it is an object of this invention to provide an apparatus which offers solution to the foregoing problems without requiring prohibitively expensive component parts.

SUMMARY OF THE INVENTION The present invention evolved, at least in part, from the realization that slippage between the copy film and the control drum is not necessarily harmful when concomitant slippage between the copy and original films is not significantly present. In fact, it has been found that allowing some slippage between copy film and drum can be beneficial in preventing slippage between the two films.

Consider the type of stretching or deformation of the films which results from light source heating as discussed above. The amount of stretching suffered by each-of the films is related to the amount of heat absorbed thereby. For example, a dark negative original tends to absorb more heat (and therefore stretch more) that the copy film lying on the drum below it. In such case it can be expected that the original will stretch more than the copy. If the copy film is frictionally bound to the drum, it will be prevented from giving with the original. Thus, a slippage between original copy results and leads to undesirable resolution loss.

The presentinvention reduces the undesirable effect of binding between the copy and the drum by providing a relatively low friction surface on the periphery of the drum. In a preferred embodiment of the invention, a pinch roller is utilized to force the original and copy films together for travel over the drum. As a result, the frictional holding force between the drum surface and the copy film is less than the frictional holding force between the original and copy films travelling over the drum. This effect has been found to produce copies of substantially improved resolution.

Further features and advantages of the invention will be more readily understood from the following detailed description when taken in conjunction with the accompanying drawings. I

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational schematic view of a film duplicating apparatus in accordance with the invention, the apparatus being shown in the initial threading stage of operation; and

' FIG. 2 is a similar view of the apparatus shown during progress of a duplicating operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT operation with the supply reels 12 and 13 full and with the various components of the apparatus in the position which they assume for convenient threading of the films 50 and 60. FIG. 2 shows the apparatus during the progress of a typical operation and after some of the film on the supply reels l2 and 13 has been subjected to the duplicating process. As shown in the Figures, a copy film 60 runs from the reel 13 over an idler roller 14 and a pinch roller 15 tothe surface of a relatively large cylindrical printing drum 16 which is rotatably mounted on the panel'l0. The film 60 proceeds to run over idler rollers 17 and 18 thence into a suitable developing chamber 19 where it is passed over idler rollers 20, 21, 22 and 23. The copy film then runs over an idler 24 and, finally, is rewound on the takeup reel 25.

The original or master film 50 runs from the supply reel 12 over idler rollers 26 and 27 and thence over pinch roller 15 where it joins the copy film 60 for passage over the drum 16. After traversing the drum, the original film 50 passes over a driven stripping roller 28, and the adjacent pinch roller 29 and is rewound on thetakeup reel 30.

The superimposed portions of the original and copy films passing over the printing drum 16 are exposed to lighting means 55 which typically includes an intense source of actinic radiation. The fundamental frequency bands of the exposing radiation will, of course, be determined by the characteristics of the copy film. In the'present embodiment, it is assumed, for example, that the copy film is of the diazo type, but the principles of the invention are equally applicable to other types of copy film. The surface area of the drumwhich instantaneously passes a given portion of original and copy film past the exposing radiation will be hereinafter referred to as the printing zone.

The pinch roller 15 is rotatably mounted on the front panel l0.and is mechanically coupled toa rotation resisting means (not shown) behind the panel in housing 11 which exerts a considerable drag against rotation of roller 15 in a clockwise direction. The drum 16 is freely rotatable on a shaft 64 (shown in dotted line) which extends axially into housing 11. In the present embodiment, the shaft 64 extends into the panel through a horizontally oriented slot 65 (shown in dotted line) which allows the drum axis freedom to toggle between positions defined by the ends of the slot. The drum axis is coupled mechanically to the toggle lever 35 which is used to control the position of the drum 16. During the film threading procedure (FIG. 1), the toggle lever is positioned such that the drum is in its rightmost orientation allowing the films to be conveniently threaded between the'pinch roller and the drum 16. After threading, the lever 35 is moved to its normal operating position, the drum moves to the left and the films 50 and 60 are pinched between the roller 15 and'the drum 16. The pinch roller 29 is mounted to toggle from left to right inthe same manner as the drum 16. Roller 29, however, is mechanically coupled to a toggle lever by which roller 29 can be moved from a left threading position (FIG. 1) to a right operating position (FIG. 2). In the operating position, the roller 29 closely adjoins the driven roller 28 as it receives the original film 50 therefrom for passage to the takeup reel 30.

In the present illustrative embodiment of the invention, the driving force which transports the films through the printing zone is provided by a motor (not shown) within housing 11 that is coupled to the stripping roller 28. The takeup reels 25 and 30 are yieldingly driven in conventional fashion by belt and pulley arrangements (not shown) which are coupled to the motor that drives the stripping roller 28. The yieldingly driven takeup reel 30 provides a light tension on the film 50 as it passes between the pinch roller 29 and the takeup reel 30. As will be appreciated, this tension is needed to prevent the formation of slack, but is not critical in determining the tension of the portion of the film 50 which is passing through the important printing zone. The yieldingly driven takeup reel 25 similarly exerts a light tension on the copy film as it passes through the developing chamber 19 and is ultimately wound on the reel 25. Since the amount of tension provided by the reels 25 and 30 is not critical, the reel mechanisms need-not be expensive high-precision components. Suitable mechanisms are disclosed in my co-pending US. application, Ser. No. 201,923 entitled Adjustable-Torque Mechanism, filed of even date herewith, and assigned to the same assignee as the present invention. The supply reels l2 and 13 are rotation-resisting reels which provide operating tension to the films 50 and 60 during their initial excursion to the point at which they are joined on the pinch roller 15. The design of the apparatus is such that the tension provided by these reels is also not particularly critical such that relatively inexpensive mechanisms can be utilized. Mechanisms suitable for use in this manner are also described in my above-referenced co-pending application.

The pinch roller 15 serves two important functions. Firstly, the roller 15 presses the joined films tightly together and against the drum 16. This action sets up the initial registration as between the films which is to be maintained during their passage through the printing zone. Secondly, the pinch roller 15 provides a relatively heavy drag on the original film 50 and establishes the tension on'the film 50 during its passage over the drum 16 and through the printing zone. The action of the pinch roller 15 establishes an isolation" of the film portions applied to the drum 16 from the relatively uncontrolled tensions of the films 50 and 60 before they are joined tightly together at the contact point between the drum l6 and the pinch roller 15. A similar isolating action is accomplished with respect to the original film 50 after passage through the printingarea by action of the pinch roller 29 pressing the original film 50 against the driven stripping roller 28. Thus, the action of the pinching rollers 15 and 29 serves to isolate the original film 50 during its passage through the printing zone from the tension-producing effect of the supply reel 12 and the takeup reel 30. By doing so, the criticality of these elements is desirably diminished. Generally, the

tension produced on a film by a rotation-resisting reel or a yieldingly driven reel is a function of the amount of film on the reel, since such amount determines the I- ever arm length. In certain prior art systems where the tension produced by such reels is critical, elaborate schemes which involve diameter-sensing arms that control variable tension-producing means on each reel are commonly utilized. The advantages of eliminating such complexities are clear.

The drum 16 is provided with a relatively low friction surface. This may be accomplished, for example, by covering the drum with a removable band of siliconeimpregnated paper. Contrary to prior approaches, it is an object of the present invention to allow the copy film to slip with respect to the drum, if such slippage is necessary to prevent the copy film 60 from slipping with respect to the original film 50. The technique of allowing only a controlled type of slippage is further advanced by maintaining the tension of the original film in the printing zone at a level which is substantially above the tension of the copy film in the zone. In this manner, a holding force as between the original film 50 and the overlapped copy film 60 is established and maintained in the printing zone. As previously indicated, the drag of pinch roller establishes a significant tension on the portion of the original film 50 in the printing area. The amount of drag produced by the roller 15 is preferably adjustable by virtue of a conventional electronic hysteresis clutch (not shown) which is controlled by the adjustment knob 40 located at the upper right hand corner of the front panel.

During normal operation of the described apparatus, the stripping roller 28 is driven in a clockwise direction as shown in FIG. 2. The pinch roller 15 establishes substantial tension on the original film 50 as it passes over the surface of the drum l6 and through the printing zone, and tends to force the original film 50 against the copy film 60 beneath it. As a result, the copy film 60 moves along with the original film 50 and acts to rotate the drum 16 which is free to turn. As above-stated, the reels and are driven in a yielding synchronism with the stripping roller 28 and act to wind the films after completion of the duplication process. Now, if we consider the effect of a heating of the master or original film 50 while in the printing zone, it is seen that if the film 50 is heated and thereby stretched, the copy film 60 is relatively free beneath it to give and thereby match movements of the master film 50 caused by heat elongation. The fact that the copy film 60 may thereby slip somewhat on the drum is of no great consequence, since the drum 16 is just incidentally rotated by the travelling films and used as a surface guide for their travel. In fact, by establishing circumstances which allow the copy film 60 to slip on the surface of drum 16,

if necessary, the problems of slippage as between the two films is diminished. Experimental operation of the disclosed apparatus yielded resolution which consistently exceeded 200 line pairs per millimeter when using film combinations that had experienced slippage with resultant double-imaging with conventional duplicating apparatus.

I claim:

1. In an apparatus for duplicating photographic film which includes a housing; a first supply reel rotatably mounted on said housing and adapted to hold original film to be duplicated; a second supply reel rotatably mounted on said housing and adapted to hold light-sensitive copy film; a drum rotatably mounted on said housing, said drum adapted to have such copy film travel over and in contact with:the periphery thereof; a roller rotatably mounted on said housing and adapted to make contact with such original film and force such original film into frictional contact with such copy film for travel therewith over said drum; a light source directed at such films travelling on said drum; first and second yieldingly-driven takeup reels; and a stripping roller rotatably mounted on said housing and adapted to make contact with such original film so as 'to 5 separate such original and copy film for travel enroute said first and second takeup reels, respectively; the improvement which comprises:

a relatively low friction surface on the periphery of said drum, said surface having a frictional holding force with respect to such copy film which is less than the frictional holding force as between such original and copy films travelling over said drum.

2. Apparatus as defined by claim 1 wherein said drum surface comprises a silicone-impregnated base material.

3. In an apparatus for duplicating photographic film which includes a housing; a first supply reel rotatably mounted on said housing and adapted to holdpriginal film to be duplicated; a second supply reel rotatably mounted on said housing and adapted to hold light-sensitive copy film; a drum rotatably mounted on said housing, said drum adapted to have such copy film travel over and in contact with the periphery thereof; a 25 roller rotatably mounted on said housing and adapted to make contact with such original film and force such original film into frictional contact with such copy film for travel therewith over said drum; first and second yielding driven takeup reels; and a stripping roller 30 rotatably mounted on said housing and adapted to make contact with such original film so as to separate such original and copy film for travel enroute said first and second takeup reels, respectively; the improvement which comprises:

a combination of a relatively low friction surface on the periphery of said drum; means for placing suchcopy film in tension, and means for controlling the tension of such original film at a level substantially above the tension of such copy film whereby the frictional holding force as between said surface and such copy film is substantially less than the frictional holding force as between such original film and copy film travelling over said drum.

4. In an apparatus for duplicating photographic film,

the combination which comprises:

a housing;

a' first rotation-resisting supply reel rotatably mounted on said housing and adapted to hold original film to be duplicated; I

a second rotation-resisting supply reel rotatably mounted on said housing and adapted to hold light sensitive copy film;

a drum rotatably mounted on said housing, said drum adapted to have copy film travel over and in contact with the periphery thereof;

a rotation-resisting pinch roller rotatably mounted on said housing and adapted to make contact with such original film and force such original film into frictional contact with such copy film for travel over said drum by pinching such films against said drum;

first and second yieldingly-driven takeup reels;

a driven stripping roller rotatably mounted on said housing and adapted to make contact with such original film so as to separate such original and copy film for travel enroute said first and second takeup reels, respectively,

material.

6. Apparatus as defined by claim 4 further comprising means for placing such copy film in tension, and means for controlling the tension of such original film at a level substantially above the tension of such copy film.

7. Apparatus as defined by claim 6 wherein said drum surface comprises a silicone-impregnated base material. 

1. In an apparatus for duplicating photographic film which includes a housing; a first supply reel rotatably mounted on said housing and adapted to hold original film to be duplicated; a second supply reel rotatably mounted on said housing and adapted to hold light-sensitive copy film; a drum rotatably mounted on said housing, said drum adapted to have such copy film travel over and in contact with the periphery thereof; a roller rotatably mounted on said housing and adapted to make contact with such original film and force such original film into frictional contact with such copy film for travel therewith over said drum; a light source directed at such films travelling on said drum; first and second yieldingly-driven takeup reels; and a stripping roller rotatably mounted on said housing and adapted to make contact with such original film so as to separate such original and copy film for travel enroute said first and second takeup reels, respectively; the improvement which comprises: a relatively low friction surface on the periphery of said drum, said surface having a frictional holding force with respect to such copy film which is less than the frictional holding force as between such original and copy films travelling over said drum.
 1. In an apparatus for duplicating photographic film which includes a housing; a first supply reel rotatably mounted on said housing and adapted to hold original film to be duplicated; a second supply reel rotatably mounted on said housing and adapted to hold light-sensitive copy film; a drum rotatably mounted on said housing, said drum adapted to have such copy film travel over and in contact with the periphery thereof; a roller rotatably mounted on said housing and adapted to make contact with such original film and force such original film into frictional contact with such copy film for travel therewith over said drum; a light source directed at such films travelling on said drum; first and second yieldingly-driven takeup reels; and a stripping roller rotatably mounted on said housing and adapted to make contact with such original film so as to separate such original and copy film for travel enroute said first and second takeup reels, respectively; the improvement which comprises: a relatively low friction surface on the periphery of said drum, said surface having a frictional holding force with respect to such copy film which is less than the frictional holding force as between such original and copy films travelling over said drum.
 2. Apparatus as defined by claim 1 wherein said drum surface comprises a silicone-impregnated base material.
 3. In an apparatus for duplicating photographic film which includes a housing; a first supply reel rotatably mounted on said housing and adapted to hold original film to be duplicated; a second supply reel rotatably mounted on said housing and adapted to hold light-sensitive copy film; a drum rotatably mounted on said housing, said drum adapted to have such copy film travel over and in contact with the periphery thereof; a roller rotatably mounted on said housing and adapted to make contact with such original film and force such original film into frictional contact with such copy film for travel therewith over said drum; first and second yielding driven takeup reels; and a stripping roller rotatably mounted on said housing and adapted to make contact with such original film so as to separate such original and copy film for travel enroute said first and second takeup reels, respectively; the improvement which comprises: a combination of a relatively low friction surface on the periphery of said drum; means for placing such copy film in tension, and means for controlling the tension of such original film at a level substantially above the tension of such copy film whereby the frictional holding force as between said surface and such copy film is substantially less than the frictional holding force as between such original film and copy film travelling over said drum.
 4. In an apparatus for duplicating photographic film, the combination which comprises: a housing; a first rotation-resisting supply reel rotatabLy mounted on said housing and adapted to hold original film to be duplicated; a second rotation-resisting supply reel rotatably mounted on said housing and adapted to hold light sensitive copy film; a drum rotatably mounted on said housing, said drum adapted to have copy film travel over and in contact with the periphery thereof; a rotation-resisting pinch roller rotatably mounted on said housing and adapted to make contact with such original film and force such original film into frictional contact with such copy film for travel over said drum by pinching such films against said drum; first and second yieldingly-driven takeup reels; a driven stripping roller rotatably mounted on said housing and adapted to make contact with such original film so as to separate such original and copy film for travel enroute said first and second takeup reels, respectively, a second pinch roller rotatably mounted on said housing for receiving such original film from said stripping roller and adapted to pinch such original film against said stripping roller, and a relatively low friction surface on the periphery of said drum, said surface having a frictional holding force with respect to such copy film which is less than the frictional holding force as between such original and copy films travelling over said drum.
 5. Apparatus as defined by claim 4 wherein said drum surface comprises a silicone-impregnated base material.
 6. Apparatus as defined by claim 4 further comprising means for placing such copy film in tension, and means for controlling the tension of such original film at a level substantially above the tension of such copy film. 